Method of treating tall oil and product obtained thereby



Patented Apr. 27, 1943 METHOD or TREATING TALL'dIL AND PRODUCT OBTAINED'THEREBY Anthony F. Oliver and Robert C. Palmenlensacola, Fla assignors to Newport Industries,

Inc., Pensacola,

Fla., a corporation of Delaware No Drawing. Application April 5, 1940,

Serial No. 328,030

4 Claims. (Cl. 260-975) This invention relates to a method of treating tall oil and to the More particularly, desulfurizing of tall oil containing sulfur,pre-

product obtained thereby.

liminary to hydrogenating tall oil, and to the desulfurized tall oil obtained thereby.

Crude tall oil, obtained as a byproduct in the manufacture of pulp by the sulfate process, is a dark, evil smelling liquid consistingof a mixture of largely unsaturated fatty acids, such as oleic, linoleic and linolenic acid, and resin acids, the fatty and resin acids being present in roughly equal proportions, together with minor propor tions of unsaponifiable matter, chiefly plant sterols. The evil smell is probably due to sulfur compounds present in the crude tall oil.

It has heretofore'been proposed to subject tall 011 to a slight amount of hydrogenation for the purpose of removing unpleasant odors therefrom. We have, however, described in our copending application, entitled Method of isolating fatty acids from tall oil, Serial No. 304,580, filed November 15, 1939, a'method of obtaining commercially valuable hard fatty acids and abietic acid from tall oil by a substantially complete hydrogenation of the tall 911, followed by fractional crystallization or distillation. This is a continuation-in-part of the earlier filed application. a

In order to obtain substantially complete hydrogenation of tall oil in a commercially economical Way, we have found that it is very desirable first to desulfurize the tall oil. The desulfurization of the tall oil cludes a decolorization of the tall oil.

Desulfurizationof tall oil in accordance with our present method maybe carried'out in a sequence of steps, one or more of which includes a simultaneous decolorizing or bleaching of, the

tall oil as a desirable-incident thereto. These steps comprise, in general, first filtering a soluthe invention relates to the.

preferably also intion of crude tall, oil in an aliphatic hydrocarhon, such as petroleum naphtha, through a stationary bed of an adsorbent medium, such as fullers earth, activatedbentonite, or other decolorizing clay or, adsorbent material, activated carbon, or the like; then, after removal of the aliphatic hydrocarbon solvent, subjecting the tall oil to a heat treatment; and finally removing the last traces of sulfur from the tall oil by reacting such sulfur with one or more heavy metals capable of forming insoluble sulfides'that can be precipitated out and filtered or otherwise removed from the tall oil.

} Both of the first two steps involve some decolorizing or bleaching effect along with a partial removal of the sulfur present: in the tall oil. All of the sulfur present cannot be economically removed from the tall oil by these first two steps, either performed separately or in conjunction with each other. However, bye/combination-of 'alljthree steps, or by the treatment with heavy metals alone, a} practically complete-re moval of sulfur' from-the tall oil can be eifected. This enables the subsequent hydrogenation step to becarried outwith an economical use of-the hydrogenation catalyst to produce a completely hydrogenated tall oil product.

It is therefore 'an important object oi this invention topro'vide a method-of desulfurizing' tall oil containing'sulfur inorder that the sub sequent hydrogenation of the fatty acid content of the tall'o'il maybe carried ftosubstantial completion witheconomic use of the hydrogenation catalyst.

It is a further important object of this invention to provide a decolorized and desulfurized tall oil, suitable for obtain hard fattyacids therefrom. I

It is a further important object of this-invention to provide a decolorized, de'sulfurized hy- Y;

drogenated tall oil'product'."

Other and further important objects of this invention will become apparent from the follow-1 ing description and appended claims.

In accordance with the present invention,

crude tall oil is subjected to a sequence of steps a for the substantially complete removal of sulfur therefrom. The initial step preferably comprises subjecting crude tall oil to filtration through a such'as an'ad bed of an adsorbent medium, sorbent clay,.as for instance fullers earth, or activated charcoahorflthe like.-' In this pre"-' liminary. treatment, a substantial amount of sul t, fur is removed from the crude tall oil, but it is not'practical to attempt to remove all of the sulfur in this step; A very substantial amount heat treatment ata temperature of around 260 to 325 C. fora period of time ranging from ,8

hours at the lowertemperatures to aslittle as I All ap-f.

10 minutes atthe higher temperatures. preciable amountof sulfur is'eliminated as hydrogen sulfide during this heat treatment, butitfi is nottfeasibleto-attempt to remove all-"of the sulfur originally present inthe crude tall oil by this heat treatment alone. A certain amount of" bleaching also takes placeduringtheheat'treat ment.

In the third, and preferably final step, the hit I traces .of sulfur are. removed by'treatmentat an elevated temperature with of forming compounds with sulfur that, are insoluble in tall oil,- particularly the so-called heavy metals, such as nickel, copper, lead, bismuth and cadmium. The treatment'with compounds of substantially use as such or for further. processing, including. a hydrogenation step, to

metals capable" Ber cent'bound rsulfur heavy metals is preferably carried out at an elevated temperature, substantially above 150 C. withan upper limit 'of 300 0., and the metallic sulfur compounds formedare precipitated out and the tall oil is cooled to a temperature of around 100 C. to facilitate itshandling'in. the subsequent step of removingthe insoluble ,metal-sulfur compounds. The precipitated sulfur compounds of the heavy. metals may'then' be removed from the tall oiLjasfby a simple filtrationstep, or by filtration 'through a. thin the insoluble sulfur compounds of the metal may be effected in any other suitableway, as by decantation, centrifuging,"or thelike. I ,The following example will serve to illustrate .a. preferredembodiment of' our invention, parts being given by weight.except iwhereotherwise specified: 7 I

ltparts of crude tall oil are dissolved injan aliphatic hydrocarbon, such as petroleum naphtha, to give an 18% solution of the crude tall oil. This solution of tall oil inlptroleum naphtha "is then filtered through a stationary bed of fullers earth containing at least an equal amount by weight of thetall oil, or 100 parts,

of fullers earth. Substantially all of the oxidized bodies and a major proportion of the sulfur compounds present in the crude tall oil are removed by this filtration step. Certain solid insoluble color bodies amounting ,to about 1.5%

of the crude tall 011 arepr'ecipitated-irom the initial petroleum-solution and may be separated by decantation prior to the filtration' through fullers earth.

I bed of fullers earth, orv other adsorbent-medium, such as activated carbon, or :a separation of The 80 parts of pale, nearly odorless tall oil, resulting from the foregoing filtration step, are next subjected to heat treatment at a temperature of 280 to 285 C. for approximately a half hour. All of the fullers earth should be completely removed from thetall oil before subjecting it to-this heat treatment step; During the heat treatment, a large part of the residual sulm fur is eliminated as hydrogen sulfide, but a morecomplete removal of hydrogen sulfide can be effected by steaming the heat treated tall oil.

Without. any substantial cooling of the tall oil, following the heat treatment step, 0.1% to 0.2% of a mixture of copper and nickel formate is added to the tall oil and heating continued at about 220 C. for hour. On addition of the copper and nickel formate, the tall oilturns black, showing the formation of sulfides of copper and nickel. The mass is then cooled to. about 100 C., ,say 105 0., and filtered through a thin bed of fuller's earth to remove the precipitated copper and nickel sulfides.

' .sequence of steps is completely freed from sul- The-extent of desulfurization effected can be controlled in some measure by the amount of fullers earth. used, although complete desulfurization is practically impossible by this means alone. A suitable ratioof fullers earth to tall oil is 2 parts to 1. Aftervfiltration through the fullersearth and after removal of, the petroleum "naphtha, an 80% yield of pale tall oil is obtained. The-20% ot'crude tall oil retained by the fullers earth consists of a black, evil smelling liquid,

somewhat more viscousthan the original crude tall oil and containing a major proportion of the sulfur present initially; I I

The following analyses will illustrate the effect or the hereinabove outlined treatment with fullers earth:

Crude talloil Specific gravity at 25 C j. 0.980 Acldyalue e 167.2 Color (Hellige Klett scale) 9L-9 Viscosity (Gardner-Holdt scale) "Q- Per cent fatty acids 52.2

. Per cent resin acids 38.8

Per cent naphthairfsolublefiun; 165

- Tall biz treated with 2 parts ere earth Per cent yield 80.0 Acid value 173.0 Color (Hellige Klett scale) 4L Viscosity .(Gardner-Holdt scale) p, M Saponification value 178.5

Ester value; l Per cent-unsaponifiable matter Per cent resin acids The tall oil obtained as a result of the above amount of copper and nickel formate, or other heavy metal compounds, required to completely remove the sulfur from tall oil will vary. Of course, depending upon the amount ofsulfur initially present. V If' crude tall 011 is directly treated with heavy metal compounds, without a preliminary filtration through an adsorbent medium and heat treatment, as much as to 1% of copper and nicke1'.-formate may be required, whereas if the tall oil has already been subjected to filtration through. an adsorbent medium and to the heattreatment step, as little as 0.1%, or. even less, of the heavy metal compounds may be required. If a lead compound, such as litharge, is used instead of the copper and nickel formates, any excess lead should'b'e completely removed to prevent poisoningof the hydrogenation catalyst. It is not necessary, when using copper and nickel, to add these in the form of their formates, since oxides of these metals can be added instead. However, better initial dispersion of the metals is obtained. if the tal oil-soluble formates are employed.

Obviously, the extentjo'i the treatment of the tall oil with iuller's earth, with-heat, and with heavy metal compounds capable of reacting to form insoluble sulfides, may be varied considerably, the intensity of one form oftreatment being compensated for by a less intense treatment in another step, ,or vice versa. Either or both of .the' first, two steps of filtering through i'ullers earthand heat treating may be completely omitted, and desulfurization effected by means of heavy metal compounds alone, or in combination. with only one of the first two steps, but not so satisfactorily as bya combination of all three steps.

The. substantially completely desulfurized tall the desulfurized tall oil is hydrogenated at a temperature of 120 to 125 C., with 1%% of a mixture of copper and nickel formate, employing a hydrogen pressure up to a maximum of 500 lbs. per sq. in. About 5 parts of mixed copper-nickel 3 to 1 mixture) formates per 300 parts of desul furized tall oil are employed. If desired, an inert solvent may be used. Other conventional hydrogenation catalystsmay be employed.

Under these conditions, absorption of hydrogen commences at a temperature of about 85 C. to 95 C., and becomes rapid at from 100 to 110 C. Most of the hydrogen is absorbed during the first hour of operation. Substantially complete hydrogenation of the fatty acid content of the tall oil is usually eii'ected under these conditions within 6 to 8 hours, about 1% by weight of hydrogen being consumed The substantially complete hydrogenation of the fatty acids in the desulfurized tall oil changes the latter from a liquid to a solid, yellowish white mass having a titre of approximately 50 C. The traces of metallic compounds contained in the hydrogenated .tall oil may be removed by dissolving the tall oil in naphtha and shaking the warmed naphtha solution with dilute sulfuric acid. Preferably the tall oil, heated to 120 to 140 C., may be treated with 0.2 to 0.3% of oxalic acid, which precipitates the small amounts of dissolved metals as oxalates which are insoluble in the oil and which may then be filtered off by any convenient method. Any excess oxalic acid may be removed by steaming the hydrogenated oil at 150 C. or thereabouts. This gives a hydrogenated tall oil free of metal impurities. The hydrogenated tall oil may also be melted and filtered, at a temperature of about 100 0., through a thin bed of fullers earth or other filter medium capable of adsorbing the small amounts of metallic compounds dissolved and of removing the suspended catalyst.

The hardened fatty acid,,viz., stearic acid, may be separated from the hydrogenated tall oil by a fractional crystallization or fractional distillation in accordance with the method disclosed in the above identified application for patent. The following table will serve to illustrate the results obtained by hydrogenating desulfurized tall oil in accordance with the above disclosed method: v

Per cent yield h'ard fatty acid 50 Acid value of hard fatty acid 190 Titre of hard fatty acid, in C 62.5 Per cent fatty acids in hard fatty acid ,(Twitchell) 94 Per cent solvent occluded by hard fatty acid matrix 56.5 Per cent residue recoverable from filtrate. I

after recovery of hard fatty acid 50.0

Acid value of residue 155 Per cent fatty acid in residue 26.5 Per cent resin acids in residue 55.5 Per cent unsaponifiable in residue 18.0

In order to establish the value of first desulfurizing tall 011 before hydrogenating it, the following oils were prepared for hydrogenation:

- (1) Crude tall oil as received.

(2) Desulfurized crude tall oil. (3) Decolorized and desulfurized tall oil.

In preparing oil (2), the crude tall oil was desulfurized completely by heating it at 260 to 270 C. for 2 hours with of mixed copper and nickel formate. The oil was then cooled to 105 C. and filtered through a thin bed of fuller's earth to removed precipitated sulfides. This oil did not further darken on heating with litharge,

by reaction with copper and nickel formate in the manner above described.

The oils were then hydrogenated at 120 to 125 C. with 1 of mixed copper and nickel formate, employing hydrogen pressures up to a maximum of 500 lbs. per sq. in. The following table gives the results obtained:

Oils subjected to hydrogenation Color (liquid) 7L-6 6 l-lL Acid value 166 160. 0 167 Titre, C Below 20 40 52 The foregoing data showsthat crude tall oil does not hydrogenate appreciablynnder conditions which give maximum hydrogenation with decolorized and desulfurized tall oil. The data also show that hydrogenation is more complete in the case of a decolorized and desulfurized tall oil than in the case of a tall 011 that has merely been desulfurized but not decolorized. There is thus shown to be true cooperation between the steps of decolorizing, with accompanying partial desulfurization, and of desulfurizing in accordance with the method disclosed herein.

Whilewe prefer to carry the hydrogenation of the desulfurized tall oil to substantial completion in order that it may have a titre above C.,

for some purposes the hydrogenation need be carried only sufficiently far to produce a hydrogenated tall oil that is solid at say 30 C.

It will, of course, be understood that various details of the process may be varied through a. wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1; In a method of preparing tall oil for hydrogenation, the preliminary step of desulfurizing said tall oil including filtering a solution of said tall oil through an adsorbent medium. heat treating the filtered tall oil for from 8 hours to 10 minutes at a temperature between 260 and 325 C., treating said heat treated tall 011 with a compound of a heavy metal at a temperature above C. to precipitate out sulfur compounds of said heavy metal, and removingthe precipitated sulfur compounds from the oil.

2. The method of desulfurizing tall 011, which comprises subjecting crude tall oil in the sequence of steps named to filtration in solution through an adsorbent earth, to heat treatment for. from 8 hours to 10 minutes at a temperature of about 260 to 325 C., to the action of a compound of a heavy metal to form an insoluble sulfur coinpound with sulfur present in said tall oil and finally to filtration to remove insoluble sulfur hours to 10 minutes at a, temperature of about 260 to 325 C., to the action of copper compounds to form an insoluble sulfur compound with sulfur present in said tall oil and finally to filtra- 5 tion to remove insoluble copper-sulfur compounds. v

v ANTHONY F. OLIVER.

ROBERT C. PALMER. 

